This invention relates to a safety lock for a window mounted for pivotal movement about a centrally disposed vertical axis and more particularly to an improved safety lock which positively limits pivotal movement of the window beyond a limited open ventilating position.
Heretofore in the art to which my invention relates, most windows installed in multi-story commercial buildings, high rise apartments and the like were fixed windows which were built from large panels of safety glass. This type window provided excellent protection against the weather and high wind loads. It also prevented tenants and other occupants of the building from accidently falling through the window. However, due to increasing power failures, air conditioning break-downs and the like, it has become necessary to install windows in such buildings which may be opened to at least a limited open emergency ventilating position without the use of special tools or keys. Such limited opening windows are usually constructed from window sashes mounted for pivotal movement about a centrally disposed vertical axis.
In most emergency situations, the person opening a pivotally mounted window is usually unfamiliar with the safety lock mounted thereon and uses excessive force to open the window. This could result in the window being opened very rapidly to a position which could possibly permit the person to fall through the window.
U.S. Pat. No. 4,080,758 discloses an intricate and complicated safety lock which is adapted to restrain pivotal movement of such a window beyond the limited open position. This safety lock utilizes a pivot arm which has a control cam eccentrically mounted at one end thereof in position to engage a leaf spring and hold the window in the limited open ventilating position. That is, the force exerted by the leaf spring against the control cam limits horizontal pivotal movement of the pivot arm, which in turn, limits movement of the window beyond the limited open position. If the window has been opened a considerable number of times or exposed to high wind loads which attempt to pivot the window beyond the limited open position, a person pushing or accidentally falling against the window could overcome the force exerted by the leaf spring and cause the window to be disengaged from the pivot arm. This would expose the person to the danger of falling through the open window. Accordingly, this safety lock provides no positive means to prevent the pivot arm from disengaging the window sash while in the limited open position.